Page images

parent body, which freely admitted the rays point it begins to give out light : precisely of light to pass through it, stopping the at this point, it begins also to exercise another calorific rays; but that caloric was not heating power, distinct from the former ; entirely intercepted, is evident from the a power which is capable of passing directly circumstance of the thermometer not falling through transparent screens, and which acts below 5o.7. Another proof that the calo- more upon a smooth black surface than on rific rays exist independently of the lumin- an absorptive white one." ous ones is, that the same results took It seems to be the general tendency of place when a flask of boiling water was caloric, to become so diffused among matter used instead of the candle. When a con- of every kind, as to produce uniformity of cave mirror of glass was substituted in place temperature. That bodies differ greatly in of the metallic reflector, little effect was the facility with which they permit the produced upon the thermometer; thus prov. motion of caloric, or transmit its effects, ing the inferiority of glass as a reflector of is matter of daily observation. The transheat.

mission of caloric in free space, or through M. Pictet endeavoured to ascertain the aeriform Auids, seems to be instantaneous, velocity with which the calorific rays moved, but in solids and liquids the case is very and for this purpose he placed the reflectors different. It may be stated as a general at a distance of sixty-nine feet from each fact, that the conducting power of any body other, having in the one focus a heated ball, is in proportion to its density ; thus, metals and in the other a delicate air thermometer. are better conductors than glass, glass than A cloth screen was interposed between the wood, and wood than feathers, wool, and reflectors, upon the removal of which the other light substances, &c. The bad conrise of the thermometer was instantaneous ; ducting power of these latter bodies, depends so that, within this distance, no perceptible upon the quantity of air enclosed within interval elapsed between the passage of the their interstices, and the force of attraction calorific

rays from one point to the other. by which this air is confined. If their Absorption, as applied to caloric, implies imperfect conducting power depended on that power which substances possess, of the difficulty with which caloric passes retaining the heating rays which impinge through their solid matter, the relative degree upon them, and thereby of acquiring an of that power would be as to the quantity elevation of temperature. The absorptive of that matter. The reverse, however, is powers of substances are very different, and the case. Thus, the reason is evident, why may be roughly said to vary directly as the wool, down, furs, &c. form such warm power of radiation. As far as the calorific articles of clothing; because, in the ordinary effect of the sun-beam is concerned, it has state in which they are employed, the effect been shewn, that the power of the absorbent of their own bad-conducting property, and body greatly depends upon its colour. that of the air retained in their interstices,

Mr. Powell, who has written several papers prevents the abstraction of caloric from the on the nature of caloric in the Philosophical body. From its porous nature, snow is a Transactions, has thus stated his views on very bad conductor, and thus forms an the subject.

admirable mantle for the protection of ve1. “ That part of the heating effect of a getables from the more intense cold of luminous hot body, which is capable of winter. being transmitted in the way of direct radi. As liquids are very easily heated, it may ation through glass, affects bodies in pro- at first sight appear that their conducting portion to their durkness of colour, without power is considerable. The very opposite reference to the texture of their surfaces. is, however, the true state of the case. The

2. “ That which is intercepted produces mobility of their particles is the chief cause a greater effect in proportion to the absorp- of their power of transmitting heat, as may tive nature or texture of the surface, without be seen from attending to the manner in respect to colour. These two characteristics which caloric acts upon them. If heat be are those which distinguish simple radiant applied to the lowest surface of any vessel heat at all intensities.

containing a liquid, the first effect produced “Thus, when a body is heated at lower will be the expansion of the particles immetemperatures, it gives off only radiant heat, diately in contact, by which their specific stopped entirely by the most transparent gravity being diminished, they will ascend glass, and acting more on an absorptive through the mass of fluid, and a fresh white surface than on a smooth black one. stratum of particles will descend to occupy

“At higher temperatures the body still their place. By a repetition of this process, continues to give out radiant heat, possessing the whole body of' fuid soon becomes exactly the same characters. But at a certain heated. But if heat be applied to the upper surface of a liquid, no such effect can take rare ; this heated air, though its tempeplace; the heated and lighter particles con- rature falls as it ascends, retains the greater tinue at the surface; and the caloric, if it part of its heat; its place at the surface is proceed downwards at all, will do so very supplied by colder air, pressing in from slowly, and must do so on the principle of every side ; and by this constant succession, absorption.

the heat is moderated, that would otherwise Count Rumford exemplified this carrying become intense. The heated air is, by the power of liquids by a very pleasing experi- pressure of the constantly ascending portions, ment. He made a solution of potash and forced towards a colder climate; as it water of the same specific gravity with descends to supply the equilibrium, it gives amber; then strewing in it some roughly out the heat it had received, and this serves powdered amber, he enclosed the whole in to moderate the extremes of cold. There a proper glass vessel, and, after exposing it thus flows a current from the poles towards to a considerable heat, placed it in a window the equator, at the surface of the earth, and to cool. As the sun shone upon the vessel, another superior current from the equator it illumirated the particles of amber, and to the poles ; and though the directions of the whole liquid was seen to be in most these are variously changed, by irregularities rapid motion, running swiftly in opposite in the earth's surface, they can never be directions, upwards and downwards at the interrupted, but, produced by general causes, same time. The ascending current occu- must always operate, and preserve, with pied the axis, the descending current the greater uniformity, the temperature of the sides of the vessel. When the sides of the globe. vessel were cooled by means of ice, the velo- Water is not less useful in this respect city of both currents was accelerated. It in the economy of nature. When a current diminished as the liquid cooled ; and when of cold air passes over the surface of a large it had acquired the temperature of the room, collection of water, it receives from it the motion ceased altogether. These currents a quantity of caloric; the specific gravity were evidently produced by the particles of the water is increased, and the cooled of the liquid going individually to the sides portion sinks. Its descent forces up a of the vessel, and giving out their caloric. portion of warmer water to the surface, The moment they did so, their specific gra- which again communicates a quantity of vity being increased, they fell to the bottom, caloric to the air passing over it; and this and of course pushed up the warmer part process may be continued for a considerable of the fluid, and so on in continuity. Count time, proportioned to the depth of the water. Rumford likewise found, that, by mixing If this is not very considerable, the whole a small quantity of starch with the water, is at length cooled to 40°, below which, so as to diminish the fluidity, it took nearly the specific gravity not increasing, the cirdouble the time to reach a certain tempe- culation ceases, and the surface is at length rature, that it did when pure water was so far cooled as to be covered with a coat used. Eider down was likewise mixed of ice. with water, which could only tend to em- The quantity of caloric afforded by water barrass the motion of the particles, and a is exceedingly great. Count Rumford says, rather more powerful effect was speedily “the heat given off to the air by each superproduced.

ficial foot of water, in cooling one degree, It is principally by the agency of Auids, is sufficient to heat an incumbent stratum elastic and non-elastic, that the distribution of air forty-four times as thick as the depth of caloric over the globe is regulated, and of the water, ten degrees. Hence, we see great inequlaities of temperature are guarded how very powerfully the water of the ocean, against; and this agency is exerted chiefly which is never frozen over except in very by the circulation of which their mobility high latitudes, must contribute to warm the renders them susceptible.

cold air which flows in from the polar Thus, the atmosphere, with which the regions." From this cause, currents must earth is surrounded, serves the important exist in the ocean similar to those formed purpose of moderating the extremes of tem- in the atmosphere. The water, which in perature in every climate. When the earth the colder regions is cooled at the surface, is heated by the sun's rays, the stratum of descends, and, spreading on the bottom of air reposing on it receives part of its caloric, the sea, flows towards the equator, which is rarefied, and ascends. At the same time, must produce a current at the surface in from a law which attends the rarefaction of the opposite direction ; and thus the ocean elastic fluids, that they become capable of may be useful in moderating the excessive containing a greater quantity of caloric at heats of the torrid zone, as well as in obvia given temperature, as they become more ating the intense cold of the polar climates.


[ocr errors]

draw straight lines from the centre to the

circumference, for meridian lines. The Of the several methods of projecting the degrees of latitude must be marked on the surface of the earth, or of a sphere, on a sides of the rhombus; but as they are plane, the globular is most esteemed, as

not of equal length, the points of division giving the most faithful and correct repre- may be found as follows:--make the sides sentation of its surface, exhibiting it with equi- of ihe rhombus, chords of the arcs of qua. distant meridians and parallels; it is, there. drants, divide each of the arcs into 90 fore, preferable to the other methods, because degrees, and through the points of division, the different countries, &c. are represented to the vertex of each quadrant, draw straight more proportional to their dimensions as

lines, and the points where they cut the they stand on the globe.

chords or sides of the rhombus, are the If, however, a cone be inscribed in a

points of division for the degrees of latitude. hemisphere, and the various circles, lines, These divisions may be found arithmeti. &c. as also the different continents and

cally as follows :--there are given the base of islands on its surface, be transferred to the

a triangle, or radius of the quadrant, and both convex surface of the cone; this will be a the angles at the base, and, therefore, that nearer approximation to the surface of a

at the vertex, to find one of the sides, one sphere than the globular projection, or than angle at the base being the given latitude, any other projection on a plane surface. and the other always 45°; hence, the sine Two such cones, so placed that their bases of the angle at the vertex, is to the base or may coincide with the equator, and their radius, as the sine of the latitude is to the axes with the axes of the sphere, will repre- required side or part of the chord corresent the whole surface of the earth, or the sponding to the given latitude. When the northern and southern hemisphere.

divisions of the latitude are found, arcs must If the surfaces of each of these cones be be drawn through them, parallel to the unwound, they will present two plane sur

equator, for the parallels of latitude, at faces, or great segments of circles, whose proper distances from each other. semidiameters are the slant heights of the Thus much for maps of the world; but cones; and if they be placed so that the for maps of any part of the earth's surface, chords of the arcs may coincide, the four either in the northern or southern hemisides of the sectors, or semidiameters of the sphere :-in order to obtain the nearest apcircles, will form a rhombus, or diamond proximation to the surface of a sphere, the square, in the middle of the figure, in which surface of the spherical zone, lying in the the name of the map or other particulars latitude of the map, should be transferred may be written.

to the surface of the frustrum of a cone, the Such a map may be constructed as semidiameters of whose greater and lesser follows:

bases, are the cosines of the latitudes of To find the length of the arc the bottom and top of the map: Let S,s, sectors ; suppose the diameter of the circle

be the sines of the latitudes of the top and to be 1, then the slant height of the cone bottom of the map, and c, C, their cosines; will be 5, hence, by Euclid, 47th P. of

then ✓ C-c + S-s the slant = .353 is the semidiameter 2

height of the frustrum, and by sine As, as of the base of the cone, and .353 X 2 X

С 3.1416 = 2.217 the length of the arc : now

C-C:N C-c + s-s :: C: as 3.1416 : 3600 :: 2.217 : 254° 9'] =

C-C length of the arc in degrees, and 360°

x C-c + S-s = the slant height 2549 9'] = 105',, 50'ļ the length of the deficient arc. Therefore, with any radius of the whole cone or radius of the greatest draw a circle, cut off from the proper side parallel of latitude, whose le igth is 3.1416 of it 105o ,, 50'}, next draw the two radii X 2 C, a proportional part of which must or sides of the sector; then, with the length be taken for the width of the map. The of the radius from the points of section, divisions of the degrees of latitude may be describe arcs intersecting one another on the found by the former trigonometrical analogy, outside of the sectors ; from the points where observing that the given base, or side of the they intersect, circumscribe the arc of the triangle, is equal to the radius of the sphere, other sector, meeting, or cutting the former; in the zone of which the frustrum of the and then finish the rhombus, by drawing cone was supposed to be inscribed, and the sides of the sector.

one of the angles at the base being the difDivide each of the arcs into 360 degrees ference of the latitude of the bottom of the for the longitude, and at proper distances map, and the given latitude whose distance 2D, SERIES.- NO. 6.

2 M

150,- VOL. XIII.

of the

[ocr errors]






is sought, and the other angle at the base mouth open downwards, and this is the is the given latitude, together with the angle barometer. whose sine is proportional to S-s. Or the When the weather is fair, and inclined to divisions may be found geometrically with to be so, the water will be level with the great ease.

section of the neck, or rather elevated above Maps constructed in the above method it, forming a beautiful concave surface will represent the different countries, &c. when disposed to be wet, a drop will more proportional to their size ; therefore, appear at the mouth, which will enlarge till greater measurements may be performed it fall, and then another drop, while the with more correctness: and if celestial maps huniidity of the atmosphere continues. The were thus construcied, they would, when degree of certainty in this instrument may properly bent, have the property of disco- be relied upon, as I have used it for many vering the stars.

years, and never found it fail in indicating Tuomas Cooke.

the same change of weather with the comDraycott, near Derby.

mon barometer.

F. H. Leadenhall Street March 14, 1831.



MR. EDITOR, SIR, OBSERVING in your excellent periodical, From the Anglo-Saxons we derive the vol. 3d, col. 830, an account of the leech names of the most ancient officers among being used as a barometer, I would beg us - of the greater part of the divisions of leave to state, with due deference to your the kingdom, and of almost all our towns correspondent's observations, that it should and villages. From them we derive our be the horse-leech found in ponds or stag- language; of which the structure, and a nant pools, instead of that used for medical majority of its words, much greater than purposes, the one being much stronger than those who have not thought on the subject the other, and more susceptible of acute would at first easily believe, are Saxon. feeling under the different changes of the Of sixty-nine words, which make up the almosphere. But although it may be amus- Lord's Prayer, there are only five not Saxon; ing to observe how the animal is affected by the best example of the natural bent of our the weather, for my own part I have never language, and of the words apt to be chosen found that degree of certainty attached to by those who speak and write it without it which I could have wished. The most design. Of eighty-one words in the solilosinple, cheap, and correct barometer, ap- quy of Hamlet, thirteen only are of Latin plicable to any useful purpose, is the fol- origin. Even in a passage of ninety words lowing:

in Milton, whose diction is more learned Take a common phial bottle; cut off the than that of any other poet, there are only rim and part of the neck. This may be sixteen Latin words. In four verses of the done by a piece of string, or rather whip- authorized version of Genesis, which contain cord, twisted round it, and pulled strongly about a hundred and thirty words, there are by two persons in a sawing position, one no more than five Latin. In seventy-nine of whom holds the bottle firmly in his left words of Addison, whose perfect taste prehand. Heated in a few minutes by the fric- served him from a pedantic or constrained tion of the string, and then dipped suddenly preference for any portion of the language, into cold water, the bottle will be decapi- we find only tifteen Latin. In later times tated more easily than by any other means. the language has rebelled against the bad Let the phial be now nearly filled with taste of those otherwise vigorous writers, pump water; applying the finger to the who, instead of ennobling their style liké mouih, turn it quickly upside-down ; on Milton, by the position and combination of removing the finger, it will be found that words, have tried to raise it by unusual and only a few drops escape. Without cork far-fetched expressions. Dr. Johnson himor stopper of any kind, the water will be self, from whose corruptions English style is retained within the bottle by the pressure of only recovering, in eighty-seven words of the external air, the weight of air without his fine parallel between Dryden and Pope, the phial being so much greater than the has found means to introduce no more than small quantity within it. Now, let a piece twenty-one of Latin derivation.---The lanof tape be tied round the middle of the guage of familiar intercourse, the terms of bottle, to which the two ends of a string jest and pleasantry, and those of necessary may be attached, so as to form a loop to business, the idioms or peculiar phrases into hang it on a nail. Let it be thus sus. which words naturally run, the proverbs, pended in a perpendicular manner, with the which are the condensed and pointed sense



of the people, the particles, on which our the speeches delivered at these anniverSyntax depends, and which are of perpetual saries, we recommend the Christian Advorecurrence ;-all these foundations of a

cate Newspaper, as containing a faithful language are more decisive proofs of the report of the transactions and sentiments Saxon origin of ours, than even the great which it records. The first in order that majority of Saxon words in writing, and the comes under our notice is the still greater majority in speaking. In all cases where we have preserved a

ANTI-SLAVERY SOCIETY. whole family of words, the superior signi- The anniversary of this truly benevolent ficancy of a Saxon over a Latin term is most institution was held at Exeter llall, (a large remarkable. “ Well-being arises from well- and commodious room lately opened in doing,” is a Saxon phrase, which may be the Strand, near Waterloo Bridge,) on thus rendered into the Latin part of the Saturday, April 23. On this occasion his language :-“ Felicity attends virtue;" but Royal Highness the Duke of Gloucester how inferior in force is the latter! In the was expected to take the chair, but having Saxon phrase, the parts or roots of words been prevented through indisposition, Lord being significant in our language, and Suiteld was called on to fill his place. familiar to our eyes and ears, throw their His Lordship's address was manly, aniwhole meaning into the compounds and mated, and unequivocal. It breathed hos. derivations, while the Latin words of the tility to slavery in all its forms, and from same import, having their roots and ele- the inhumanities inseparable from the sysments in a foreign language, carry only a tem, still practised in our colonies, his conventional signification to an English ear. Lordship argued the necessity of a total It must not be a subject of wonder that abolition. language should have any closer connexion T. Fowel Burton, Esq., M. P. drew with the thoughts and feelings which it a frightful picture of this colonial monster, denotes, than our philosophy can always establishing his general view by an appeal explain. As words convey these elements to facts, some of which consign to the of the character of each particular mind, so gibbet of infamy a clergyman of Jamaica, the structure and idioms of a language, those named Brydges, for his inhumanity toproperties of which, being known to us only wards one of his slaves. This detestable by their effect, we are obliged to call its system, he asserted, has within a few years spirit and genius, seem to represent the destroyed no less than forty-five thousand character or assemblage of quality which human beings. distinguish one people from others. - Lard

Sir James Mackintosh argued forcibly ner's Cabinet Cyclopedia.

on the necessity of a total abolition. Little had yet been done; but from the new Parliament, about to be returned, much might be expected.

Dr. Lushington avowed himself to When the tide of benevolence first began be an advocate for the immediate and to flow, many persons who watched its pro- entire emancipation of West India slaves. gress, hesitated not to predict that it was Of every candidate soliciting to be returned nothing more than a momentary effer- to Parliament, he recommended that each vescence, which would speedily expend voter should ask the question-do you its energy, and subside. Time, however, abhor slavery ? will you vote for its exterhas proved, that false prophets may exist, mination ?" and unless his answer without taking shelter under the sanction of prompt and unequivocal, to vote against religion. Instead of diminishing, these him. societies increase in number; instead of The Rev. Daniel Wilson was an enemy having expended their energies, they ac- to slavery on religious grounds, and was quire renewed vigour; instead of contract- resolved to co-operate in any measures that ing their spheres of operation, they occupy should tend to annihilate the horrid system. a wider field, embrace new objects, and Daniel O'Connell, Esq. 11. P. declared every year their supporters become more himself the mortal foe of slavery, abhorring

it in all colours, creeds, and climes. He Amounting in their varied forms to asseried, that in fourteen colonies, during about one hundred, we must content our- only ten years, there had been a decrease selves with noticing some of the principal; in population of forty-five thousand eight for beyond this, our limits will not allow us hundred and one. Every day ten human to pass. To such of our readers, however, beings are despatched by slavery. It could as wish to obtain an extended outline of be borne no longer, and he was resolved





« PreviousContinue »